The numbers here are historical averages based on climate data gathered at the San Diego International Airport, located on San Diego Bay near the city center.

Temperature

76 °F

September average high

24 °C

65 °F

September average low

18 °C

In most years, San Diego averages a daily maximum temperature for September that's between 73 and 79 degrees Fahrenheit (23 to 26 degrees Celsius). The minimum temperature usually falls between 63 and 67 °F (17 to 20 °C).

The days at San Diego begin to cool down during September. By the end of the month, the temperature has dropped around 3 °F (1.5 °C) below what it was at the start.

27 days

70 °F max. or more (21 °C)

27 days

70 °F min. or less (21 °C)

Nearly every day in September warms to over 70 °F (21 °C) in San Diego. The city averages 6 days this month when the thermometer reaches into the 80s °F (over 26 °C). Temperatures above 90 °F (32 °C) occur during September just once every few years.

At night, the thermometer dips to 60 °F (16 °C) or below on 2 days. But September does not normally get as cold as 50 °F (10 °C).

Rain

0.2 in

total precipitation

4 mm

1 day

of rain

Most years, San Diego gets less than 0.2 inches (6 mm) of rain in September. About once every four years, the city receives no rain at all this month.

Sun

69 %

sunshine

15 days

clear skies

The sun's rays reach the ground in San Diego during 69 percent of daylight hours on average in September, for a total of 255 hours in the month. Typically on 15 days this month the sky is mainly clear, with at most 30 percent cloud cover.

Sunlight in September at San Diego lasts for 12 hours and 20 minutes a day on average. The longest day of the month is the 1st with 12 hours and 49 minutes of daylight. By the end of the month, the days have shortened to 11:52 from sunrise to sunset. These durations can vary by a minute or two from year to year.

Humidity

73 %

September average humidity

The relative humidity in San Diego during September usually peaks at 80 percent just after midnight then drops to 62 percent by early afternoon.

Local Time

1 am

4 am

7 am

10 am

1 pm

4 pm

7 pm

10 pm

Humidity %

80

80

77

66

62

65

74

78

Wind

7.1 mph

September wind speed average

11.4 kph

September is an average month in San Diego for wind speed.

Storms

0 days

rainfall of 0.5 inches (13 mm) or more

0 days

with thunderstorms in September

Just once a decade does San Diego have a day in September when it gets as much as one-half to one inch (13 to 25 mm) of rain.

San Diego has a thunderstorm during September about once in five years.

Reference

These weather data are long-term historical averages provided by the National Climatic Data Center of the United States. The temperature and precipitation numbers are 1981-2010 normals while the humidity and thunderstorm statistics are 1961-1990 normals.